Size reduction and performance improvement are strongly required of digital still cameras, digital video cameras and the like (simply referred to as digital cameras, hereinafter) each provided with an image sensor for performing photoelectric conversion. In particular, from a convenience point of view, a digital camera is strongly desired which employs a zoom lens system having a high zooming ratio and being able to cover a wide focal-length range from a wide angle condition to a high telephoto condition. On the other hand, in recent years, a zoom lens system is also desired which has a wide angle range where the photographing field is large.
As zoom lens systems having a high zooming ratio and zoom lens systems having a wide angle range, there have conventionally been proposed various kinds of zoom lenses each having a four-unit configuration of positive, negative, positive, and positive, in which a first lens unit having positive optical power, a second lens unit having negative optical power, a third lens unit having positive optical power, and a fourth lens unit having positive optical power are arranged in order from the object side to the image side.
Japanese Laid-Open Patent Publication No. 2009-139701 discloses a zoom lens having the above-mentioned four-unit configuration of positive, negative, positive, and positive. In this zoom lens, at the time of magnification change from a wide-angle limit to a telephoto limit, at least a first lens unit, a second lens unit, and a third lens unit move and thereby the intervals between the respective lens units vary. The first lens unit is composed of one lens element. The third lens unit includes two lenses, a positive lens and a negative lens. The relation between a ratio of the amount of axial movement of the first lens unit at a telephoto limit relative to at a wide-angle limit to the amount of axial movement of the third lens unit at a telephoto limit relative to at a wide-angle limit, and a ratio of the maximum length of the lens in the third lens unit to the maximum length of the lens in the fourth lens unit, each maximum length being measured from one end to the other end of the lens along a straight line that is orthogonal to the optical axis and includes the position where the optical axis passes, is set forth.
Japanese Laid-Open Patent Publication No. 2009-098458 discloses a zoom lens having the above-mentioned four-unit configuration of positive, negative, positive, and positive. In this zoom lens, at the time of magnification change from a wide-angle limit to a telephoto limit, at least a first lens unit, a second lens unit, and a third lens unit move and thereby the intervals between the respective lens units vary. A ratio of the sum of the axial thicknesses of the respective lens units, to the focal length of the entire zoom lens at a telephoto limit, is set forth.
Japanese Laid-Open Patent Publication No. 2009-047986 discloses a zoom lens having the above-mentioned four-unit configuration of positive, negative, positive, and positive. In this zoom lens, at the time of magnification change from a wide-angle limit to a telephoto limit, at least a first lens unit, a second lens unit, and a third lens unit move and thereby the intervals between the respective lens units vary. The relation between the Abbe number and the partial dispersion ratio of at least one lens in the positive lens unit arranged on the object side relative to a diaphragm, is set forth.
Japanese Laid-Open Patent Publication No. 2008-191291 discloses a zoom lens having the above-mentioned four-unit configuration of positive, negative, positive, and positive. In this zoom lens, at the time of magnification change from a wide-angle limit to a telephoto limit, at least a first lens unit, a second lens unit, and a third lens unit move and thereby the intervals between the respective lens units vary. The positive lens unit arranged on the object side relative to a diaphragm includes a cemented lens obtained by cementing a plurality of lenses. The relation between the Abbe number and the partial dispersion ratio of at least one lens constituting the cemented lens, is set forth.
Japanese Laid-Open Patent Publication No. 2008-102166 discloses a zoom lens having the above-mentioned four-unit configuration of positive, negative, positive, and positive. In this zoom lens, at the time of magnification change from a wide-angle limit to a telephoto limit, at least a first lens unit, a second lens unit, and a third lens unit move and thereby the intervals between the respective lens units vary. The first lens unit is composed of two lenses. The third lens unit is composed of, in order from the object side, two lenses, a positive lens and a negative lens. A ratio of the axial thickness of a positive lens to the axial thickness of a negative lens in the first lens unit is set forth.
Japanese Laid-Open Patent Publication No. 2007-271711 discloses a zoom lens having the above-mentioned four-unit configuration of positive, negative, positive, and positive. In this zoom lens, at the time of magnification change from a wide-angle limit to a telephoto limit, at least a first lens unit, a second lens unit, and a third lens unit move and thereby the intervals between the respective lens units vary. The first lens unit is composed of two or less lenses including a positive lens. The second lens unit includes, in order from the object side to the image side, a negative lens, a compound lens comprising two optical members having refractive powers of different signs, and a positive lens.
Japanese Laid-Open Patent Publication No. 2007-212537 discloses a zoom lens having the above-mentioned four-unit configuration of positive, negative, positive, and positive. In this zoom lens, at the time of magnification change from a wide-angle limit to a telephoto limit, at least a first lens unit, a second lens unit, and a third lens unit move and thereby the intervals between the respective lens units vary. A ratio of the distance from the vertex of an object side surface of a lens arranged closest to the object side in the first lens unit to the vertex of an object side surface of a lens arranged closest to the object side in the third lens unit, at a zoom position where the first lens unit is positioned closest to the image side at the time of zooming, to the focal length of the entire lens system at the zoom position, is set forth.
Japanese Laid-Open Patent Publication No. 2007-047538 discloses a zoom lens having the above-mentioned four-unit configuration of positive, negative, positive, and positive. In this zoom lens, at the time of magnification change from a wide-angle limit to a telephoto limit, at least a first lens unit, a second lens unit, and a third lens unit move and thereby the intervals between the respective lens units vary. The first lens unit comprises, in order from the object side to the image side, a negative lens and a positive lens. The second lens unit includes at least one positive lens. The relation between the amount of axial movement of the first lens unit at a telephoto limit relative to at a wide-angle limit, and a ratio of the focal length of the entire lens system at a wide-angle limit to the focal length of the entire lens system at a telephoto limit, is set forth.
Japanese Laid-Open Patent Publication No. 2006-171055 discloses a zoom lens having the above-mentioned four-unit configuration of positive, negative, positive, and positive. In this zoom lens, at the time of magnification change from a wide-angle limit to a telephoto limit, at least a first lens unit, a second lens unit, and a third lens unit move and thereby the intervals between the respective lens units vary. The first lens unit comprises, in order from the object side, one negative lens and one positive lens. The second lens unit comprises, in order from the object side, two negative lenses and one positive lens. The third lens unit comprises three or less lenses. A ratio of the focal length of the third lens unit to the focal length of the fourth lens unit is set forth.
Japanese Laid-Open Patent Publication No. 2005-181499 discloses a zoom lens having the above-mentioned four-unit configuration of positive, negative, positive, and positive. In this zoom lens, at the time of magnification change from a wide-angle limit to a telephoto limit, at least a first lens unit, a second lens unit, and a third lens unit move and thereby the intervals between the respective lens units vary. The first lens unit comprises one positive lens and one negative lens. The third lens element includes, in order from the object side, at least a positive lens and a negative lens. At least the positive lens in the third lens unit is a spherical lens. A lens positioned closest to the image side in the third lens unit has at least one aspheric surface.